Method for monitoring the availability of at least one memory element that is assigned to an electric unit

ABSTRACT

A method for monitoring the operating readiness of memory elements which are assigned to an electronic unit, an engine control unit for example. Furthermore, an electronic unit for executing the method and a computer program, as well as a computer program product are described. In the method described, a supply voltage of the electronic unit is monitored to ensure error-free operation of the memory elements.

FIELD OF THE INVENTION

The present invention relates to a method for monitoring the operatingreadiness of at least one memory element that is assigned to anelectronic unit, and an electronic unit for executing the method. Thepresent invention also relates to a computer program for executing themethod according to the present invention.

BACKGROUND INFORMATION

Flash EPROMs, for example, are used for the storage of program code inelectronic units such as, for example, engine control units. It is alsocommon in modern controllers to integrate flash memory elements toexecute programs as quickly as possible. However, the integrated flashmemory element is substantially more expensive than an external flashmemory IC (integrated circuit) which, however, is slower in comparisonwith the former. For this reason, external (stand-alone) flash memoryICs are used for program sections which do not affect the performance ofthe overall system.

This creates the problem that different technologies are used tomanufacture the different ICs for the computers and the memories whichtherefore run on different operating voltages. Even on the computer,depending on the technology, the operating voltages for the computerkernel and the operating voltage of the flash memory may be different.

Generally, the operating voltage of the flash memory is higher than thatof the computer kernel. However, program execution is ensured only whenthe operating voltage for the memory in which the program to be executedis stored and the operating voltage for the computer kernel are within aspecified tolerance zone.

Low voltage recognition of the operating voltages and associated errorhandling are necessary for a supply voltage dip of the engine controlunit.

A method and a device for monitoring an electronic computing unit aredescribed in German Patent Application No. DE 196 01 804. In the methoddescribed, in the event of an interruption in the supply voltage andfollowing initialization of the computing unit, a reset signal istransmitted from a voltage monitoring device to the computing unit and,after the signal is received, the operating state of the computing unitis checked by comparing a content of a volatile memory cell with afixedly predefined code. A decision regarding the further controlsequence is made based on this check. After triggering a reset signal,the content of a volatile memory cell is compared with a predefinedcode. Each reset signal thus triggers a check during which a test ismade on whether the content of the volatile memory is still completelypresent. This makes it possible to differentiate between interruptionsin the voltage supply which cause errors in the computing unit and suchinterruptions in the voltage supply which do not cause errors in thecomputing unit.

Depending on the size of a dip in the supply voltage it may occur thatthe highest operating voltage is no longer sufficient for part of theflash memory, but the other operating voltages for the other parts ofthe flash memory and the computer kernel are still within the specifiedtolerance. Normal program execution is thus no longer possible underthese circumstances because it is assumed that the entire flash memorymust always be available.

A low voltage on the operating voltage is normally detected via athreshold value using hysteresis. However, a prerequisite for this isthat the threshold value is higher than the memory's minimum operatingvoltage, but also lower than the lowest operating voltage caused byinterruptions. Such an analysis is indeed no longer possible when theflash memory's operating voltage has a very narrow tolerance.

SUMMARY

An example method according to the present invention may be used formonitoring the operating readiness of at least one memory element thatis assigned to an electronic unit. The operating readiness of the memoryelement or memory elements is checked by monitoring the electronicunit's supply voltage. The error-free operation of the entire electronicunit may be ensured in this way.

The example method according to the present invention may make itpossible in particular to monitor multiple memory elements, external aswell as internal elements, which require different operating voltages,and makes it also possible to make an assertion about which of thedifferent memory elements are still operational at a certain supplyvoltage.

Instead of monitoring the operating voltage or operating voltages of theat least one memory element, the supply voltage of the electronic unit,e.g., an engine controller, is thus monitored. This makes it possible todetect the shortfall of the operating voltage at the at least one memoryelement in a timely manner.

The analysis of the threshold value shortfall, by using a providedcomputing unit for example, may take place in different ways, dependingon the accuracy and response time requirements and also as a function ofthe overall concept for the engine controller.

One approach provides that the supply voltage is initially divided down.The supply voltage divided down may then be preferably cyclicallymeasured using an analog-digital converter (ADC), for example,cyclically read in (polling) at a general purpose input of the computingunit and/or analyzed at an interrupt input of the electronic computingunit.

Another approach provides that the supply voltage is entered into acomparator whose output signal is analyzed for monitoring the supplyvoltage. The analysis takes place, for example, in that the outputsignal is cyclically read in (polling) at a general purpose input of theelectronic computing unit and/or analyzed at an interrupt input of theelectronic computing unit.

An embodiment of the present invention provides that the operatingvoltage of the at least one memory element is additionally monitored.

If, for example, multiple memory elements are provided which requireoperating voltages of varying intensity, then, in the event of detectionof a low voltage at one of the memory elements, the computing unit mayonly process program code from memory elements to which an adequateoperating voltage is applied. This makes it possible, in a motor vehiclefor example, to continue to ensure a limited functionality (e.g., at thestart). As soon as it is detected that the operating voltage is in thespecified range for all memory elements or for all parts of a memoryelement, e.g., of a flash memory element, the entire program code may bere-utilized.

An example electronic unit according to the present invention, e.g., anengine control unit, is operated using a certain supply voltage. Atleast one memory element is assigned to the unit. Memory elements may beflash memory elements but also other known memory elements; memoryelements of a different type may also be used. The electronic unit isdesigned in such a way that, for monitoring the readiness for operationof the at least one memory element, monitoring of the electronic unit'ssupply voltage is provided.

A suitable device is used for monitoring that, based on the monitoredelectronic unit's supply voltage, allows the determination as to whichof the memory elements is operational. The reliable operation of theentire electronic unit may thus be ensured.

The electronic unit preferably has a computing unit, e.g., amicroprocessor or a controller.

An example embodiment of the present invention provides ananalog-digital converter (ADC) for monitoring the supply voltage. Analternative design provides a comparator for monitoring the supplyvoltage.

A design is of course possible in which a comparator as well as ananalog-digital converter are provided, so that the different methods formonitoring the supply voltage may be combined in any way to achieve adesired redundancy.

An example computer program according to the present invention includesprogram code means to execute an above-described method. This method isexecuted on a computer or a suitable computing unit. The computing unitis preferably an electronic computing unit in an electronic unitaccording to the present invention.

An example computer program product according to the present inventionprovides that the program code means are stored on a computer readabledata medium.

It shall be understood that the above-mentioned features and thefeatures which will be explained below are usable not only in thecombination cited, but also in other combinations or alone withoutleaving the scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated in the drawing based on exemplaryembodiments and is explained in greater detail in the following withreference to the drawing.

FIG. 1 shows an example embodiment of the electronic unit according tothe present invention in a schematic representation.

FIG. 2 shows an example embodiment of the method according to thepresent invention in a flow chart.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

An electronic unit according to an example embodiment of the presentinvention, an engine control unit 10 in this case, is schematicallyillustrated in FIG. 1. Shown here are an electronic computing unit 12,namely a controller 12, an analog-digital converter (ADC) 14, acomparator 16, a first memory element 18, and a second memory element20. Memory elements 18 and 20 are flash memory elements 18 and 20 inthis case.

Controller 12 has a general purpose input 22 and an interrupt input 24.The required operating voltage of controller 12 differs from therequired operating voltages of first and second memory elements 18 and20, which in turn require operating voltages of different intensity.

The supply voltage of engine control unit 10 is used for monitoring theoperating readiness of both memory elements 18 and 20. This offersvarious possibilities. At first, the supply voltage of engine controlunit 10 may be divided down, and the supply voltage divided down maythen be measured using ADC 14, read in at general purpose input 22and/or analyzed at interrupt input 24.

Alternatively or also additionally, the supply voltage may be enteredinto comparator 16 whose output signal is then preferably cyclicallyread in at general purpose input 22 for analysis or analyzed atinterrupt input 24.

A method according to the present invention is represented in FIG. 2 ina flow chart. In a step 30, engine control unit 10 is started up. Formonitoring the operating readiness of both memory elements 18 and 20,the supply voltage of engine control unit 10 in monitored in a step 32.If, based on the supply voltage, it is detected that, for example, justfirst memory element 18 is operational, controller 12 will only read outand process program code from this memory element 18 in a step 34 untilthe operating voltage of second memory element 20 is also in thespecified range again.

If monitoring does not yield a value below threshold, then program codefrom both memory elements 18 and 20 is continued to be processed in astep 36.

A particular advantage of the method according to the present inventionlies in the fact that the demands on the supply voltage of enginecontrol unit 10 are lower than on the operating voltages of memoryelements 18 and 20 since temporary voltage dips may be bypassed, e.g.,at the start of the motor vehicle, in particular when the battery isweak, and/or during operation.

1-16. (canceled)
 17. A method for monitoring an operating readiness oftwo memory elements assigned to an electronic unit, comprising:monitoring a supply voltage of the electronic unit; operating each ofthe memory elements using an operating voltage that is differentcompared to the supply voltage, each of the operating voltages being ina specified range so that the respective memory element is operational;and detecting, based on the monitoring of the supply voltage, that theoperating voltage of one of the two memory elements is not in thespecified range, and processing program code from the other are of thetwo memory elements whose operating voltage is in the specified range.18. The method as recited in claim 17, wherein the monitoring of thesupply voltage includes initially dividing down the supply voltage. 19.The method as recited in claim 18, wherein the monitoring of the supplyvoltage includes cyclically measuring the divided down supply voltageusing an analog-digital converter.
 20. The method as recited in claim18, wherein the monitoring of the supply voltage includes cyclicallyreading in the divided down supply voltage at a general purpose input ofan electronic computing unit.
 21. The method as recited in claim 18,wherein the monitoring of the supply voltage includes analyzing thedivided down supply voltage at an interrupt input of an electroniccomputing unit.
 22. The method as recited in claim 19, wherein themonitoring of the supply voltage includes entering the supply voltageinto a comparator whose output signal is analyzed.
 23. The method asrecited in claim 22, wherein the monitoring of the-supply voltageincludes cyclically reading in the output signal of the comparator at ageneral purpose input of an electronic computing unit.
 24. The method asrecited in claim 22, wherein the monitoring of the supply voltageincludes analyzing the output signal of the comparator at an interruptinput of an electronic computing unit.
 25. The method as recited inclaim 17, monitoring the operating voltage of the at least one of thememory elements.
 26. An electronic unit that is using a supply voltage,comprising: two memory elements assigned to the electronic unit, each ofthe memory elements being operated using an operating voltage that isdifferent than the supply voltage, each of the operating voltages beingin a respective, specified range so that the respective memory elementis operational; and a monitor to monitor the supply voltage, whereinbased on the monitoring of the supply voltage, when the electronic unitdetects that the operational voltage of one of the two memory elementsis no longer in its respective specified range, program code isprocessed from the memory element when operating voltage is in itsrespective specified range.
 27. The electronic unit as recited in claim26, further comprising: an electronic computing unit.
 28. The electronicunit as recited in claim 26, wherein at least one of the memory elementsis a flash memory element.
 29. The electronic unit as recited in claim26, wherein the monitor includes an analog-digital converter to monitorthe supply voltage.
 30. The electronic unit as recited in claim 26,wherein the monitor includes a comparator to monitor the supply voltage.31. A computer program, comprising: program code configured to beexecuted on a computing unit, the program code configured to monitor anoperational readiness of two memory elements assigned to an electronicunit, the program code, when executed by the computer unit, causing thecomputing unit to perform the following steps: monitoring a supplyvoltage of the electronic unit; operating each of the memory elementsusing an operating voltage that is different compared to the supplyvoltage, each of the operating voltages being in a specified range sothat the respective memory element is operational; and detecting, basedon the monitoring of the supply voltage, that the operating voltage ofone of the two memory elements is not in the specified range, andprocessing program code from the other are of the two memory elementswhose operating voltage is in the specified range.
 32. A computerreadable data medium storing a computer program, the computer programincluding: program code configured to be executed on a computing unit,the program code configured to monitor an operational readiness of twomemory elements assigned to an electronic unit, the program code, whenexecuted by the computer unit, causing the computing unit to perform thefollowing steps: monitoring a supply voltage of the electronic unit;operating each of the memory elements using an operating voltage that isdifferent compared to the supply voltage, each of the operating voltagesbeing in a specified range so that the respective memory element isoperational; detecting, based on the monitoring of the supply voltage,that the operating voltage of one of the two memory elements is not inthe specified range, and processing program code from the other are ofthe two memory elements whose operating voltage is in the specifiedrange.